Vacuum relay having improved contact electrodes



p 27, 1966 v. E. DE LUCIA 3,275,783

VACUUM RELAY HAVING IMPROVED CONTACT ELECTRODES Filed May 17, 1965 Glass Victor E. DeLucio,

INVENTOR.

yak 0 M ATTORNEY.

United States Patent 3,275,783 VACUUM RELAY HAVING IMPROVED CONTACT ELECTRODES Victor E. De Lucia, 927 Euclid Ave., Santa Monica, Calif. Filed May 17, 1965, Ser. No. 456,318 7 Claims. (Cl. 200-166) The present invention relates to electrical relays, and it relates more particularly to relays of the vacuum type which have their operating components enclosed in an evacuated envelope.

The type of relay with which the invention is concerned is particularly advantageous in that it can be used for high voltage applications, and when so used, it can be operated for relatively long periods of time without any appreciable contact deterioration.

The particular vacuum relay to be described includes a movable armature and magnetic pole pieces enclosed in an evacuated envelope. The energizing coil for the relay, and the major portion of its magnetic circuit, however, are mounted externally of the envelope. Such a construction is advantageous in that the relay is sensitive because its magnetic circuit projectsdirectly into the evacuated envelope. However, since most of the magnetic material is outside the envelope, the out-gassing problems are minimized.

The prior art vacuum relay of the general type with which the present invention is concerned was found to deteriorate when used with extremely high voltages and peak currents, and especially under conditions of high ambient temperatures. These failures of the prior art relays have been found to be generally due to the following conditions:

(a) Loss of vacuum in the envelope due to out-gassing of the metallic components within the envelope;

(b) A diffusion of gases into the evacuated envelope at high operating temperatures through the metal seals on the envelope;

(c) Diffusion of gases at the glass-metal interfaces due to solarization in the glass;

(d) Chemical break-down of the glass in the envelope, for example, a break-down of the sodium and potassium components, under the influence of charged ions in the high electrostatic fields created in the envelope;

(e) Metallic sputtering of the metal contact material upon the inn-er wall of the envelope, thereby creating electrically conductive paths and producing micro-arcing between terminal pins extending'through the glass, which micro-arcing accelerates the conditions set forth in paragraphs (0) and (d) (supra).

An object of the present invention, therefore, is to provide an improved vacuum relay which is constructed so that the above listed conditions are eliminated, or diminished, so as to increase the reliability of the relay, espe- As mentioned above, a limitation in the operation of the prior art vacuum relay has been found to arise due to the deposition of metallic vapors upon the inner wall of the evacuated envelope of the relay so as to form conductive film. These metallic vapors are created within the envelope by sputtering and vaporization of the metal- Patented Sept. 27, 1966 ICC lie contacts during their high current switching operation.

In order to reduce such vaporization of the metallic contacts, the contacts of the improved relay of the invention are formed of a material having an extremely high melting point and having extremely low vapor pressure. For example, copper in filtrated tungsten has been found to be ideal for the purpose; such contacts having the additional feature of exhibiting relatively good electrical conductivity characteristics.

An additional advantage in the use of the contact material referred to in the preceding paragraph resides in the fact that the contacts formed of such material have been found to exhibit less tendency to weld together under peak direct-current switching operations as compared, for example, to molybdenum.

Contact arcing is further reduced in the improved relay to be described by the provision of a spring-loaded hinge assembly between the movable contact of the relay and the terminal pin for that contact.

In addition, appropriate shields are provided in the relay to be described, so that any residual contact vaporization which might occur is not permitted to reach the surface of the envelope so as to condense thereon.

As mentioned above, the metallic condensate in regions on the envelope surface where high voltage gradients exist permits micro-arcing to occur. This micro-arcing, as explained, creates chemical break-down of the glass which causes its sodium and potassium components to destroy the high vacuum within the envelope. This, in turn, degrades the ability of the relay to withstand the kilovoltage applied across its contacts under its usual working conditions. The degradation can become such that a glow discharge is created with the relay there-by rendering the relay completely inoperative.

In the usual prior art relay of the type under consideration, ion bombardment in the areas of the glass envelope adjacent the terminal pins is most severe. Solarization of the glass in these areas causes minor undetectable leaks in the glass-metal seals.

In the embodiment to be described, a small shield composed, for example, of titanium, is mounted on each terminal pin in position to shield the aforesaid areas of the glass adjacent the pins. These shields'not only prevent solarization of the glass around the terminal pins, but also shield the glass from metallic deposition. The ionic bombardment of the shields actually assists in lowering the pressure in the envelope due to the ionic pumping phenomenon.

Further objects and advantages of the invention will become apparent from a consideration of the following description, when the description is taken in conjunction with the accompanying drawings, in which:

, FIGURE 1 is a side sectional view showing a vacuum relay constructed in accordance with the concepts of the present invention;

FIGURE 2 is a cross-sectional view, on an enlarged scale, taken substantially along the line 22 of FIG- URE 1; and

FIGURE 3 is an enlarged fragmentary perspective view showing certain of the internal components of the improved relay of the present invention.

As illustrated in the drawing, the vacuum relay comprises an evacuated envelope 10. This envelope may be formed of glass, or other appropriate material, and it is closed at its lower end by a metallic wall which, with the glass envelope, defines the evacuated chamber.

A magnetizable core 12 is mounted at the end of the envelope 10 and forms a portion of the metallic end wall. The magnetizable core extends on both sides of the envelope. An armature 14 is pivotally mounted within the evacuated chamber for movement towards and away from the inner surface of the core 12, upon energization and de-energization of the relay. An electric coil 16 is mounted within the core structure externally of the envelope.

A spring 18 normally biases the armature 14 to the tilted condition shown in FIGURE 1. However, when the coil 16 is energized, the resulting magnetism established in the core 12 causes the armature 14 to be drawn down against the core, and against the biasing action of the spring 18.

A movable contact 20 is mounted on one end of an insulating rod 22 which, in turn, is supported on the armature 14 by means of an appropriate clip 24. The movable contact 20, as best shown in FIGURE 3, is mounted on the upper end of the rod 22 by means of an appropriate U-shaped bracket 26.

The rod 22 may be formed of sapphire, or other appropriate insulating material. In order to prevent a discharge glow of the sapphire rod 22 due to ionic bombardment, and to reduce the possibility of secondary emission and resulting degradation of the relay, the portion of the rod 22 adjacent the bracket 26 may be coated with a suitable metal, such as silver.

The movable contact 20 is in the form of a strip, composed, for example, of molybdenum. One end of the movable contact extends into a slot formed in the end of a first terminal pin 30 which extends radially through the envelope 10. The movable contact 20 makes selective contact with a second terminal pin 32 which also extends radially through the envelope 10.

A glass stop 34 protrudes from the envelope t-o form a stop for the movable contact, when the relay is of the single-pole, single-throw type.

The movable contact 20 has a contact button 20a formed in the end thereof which makes selective contact with the terminal pin 32. This contact button 20a may be mounted on the movable contact 20 by forming a hole in the movable contact, and by mounting the button 20a in the hole and silver brazing it to the movable contact.

The button 20a itself may be formed, for example, of copper infiltrated tungsten. This material is used in the contacts of the relay of the invention, since they exhibit relatively high electrical conducting characteristics, and yet have a low vapor pressure, so that vaporization of the contacts is reduced to a minimum, for the purposes expressed above.

The inner ends 30a and 32a of the respective terminal pins 30 and 32 are also formed, for example, of copper infiltrated tungsten, for the purposes expressed above. The remaining portions 30b and 32b of the respective contacts may be formed, for example, of molybdenum. The two portions of each of the contacts may be joined together by a silver braze, or other suitable means.

As mentioned above, the low contact resistance and low vaporization of the copper infiltrated tungsten contacts reduces the vaporization of metal within the relay to a minimum, and thereby obviates any deposition of metal on the inner wall of the relay envelope, so that microarcing between the terminal pins along the inner surface of the relay walls is prevented.

The movable contact 20 is retained in the slot at the end of the terminal pin 30 by means of a resilient strip 50 which has a U-shaped configuration, as shown, and which is affixed at its remote end to the strip 20. This strip 50 forms a spring which holds the movable contact firmly in the slot in the terminal pin 30, so as to prevent arcing as the movable contact is pivoted back and forth by the armature 14.

During the assembly of the relay, the right hand end of the spring strip 50 may be tacked to the movable contact 20 by a spot weld, and may then be shaken free, when the movable contact is in place.

A pair of disc-like shields 52 and '54 may be mounted on the terminal pins 32 and 30 adjacent the surface of the envelope 10. These shields may be formed, for example, of titanium, and they may have a disc-like configuration. For example, each shield may be of the order 4+ of .005 inch thick, and about 0.250 inch in diameter. The shields are mounted concentrically on the respective terminal pins to shield the glass area around the pin, for the reasons explained above. The shields may be spot welded to the respective pins.

Likewise, the contact button 20a on the movable contact 20 may be surrounded by a cylindrical shield 56. This latter shield may be formed of molybdenum, for example, and it is brazed or welded to the movable contact to surround the button 20a. The shield 56 prevents any residual vaporized metal which may be produced during the operation of the relay from being emitted to the walls of the relay.

The invention provides, therefore, an improved vacuum relay which is constructed so that it may operate satisfactorily, and over long periods of time, in conjunction with extremely high voltages and peak currents, and under high temperature ambient conditions.

While a particular embodiment of the invention has been shown and described, modifications may be made. The following claims are intended to cover all modifications which fall within the scope of the invention.

What is claimed is:

1. In a vacuum relay which includes an envelope, a magnetic member mounted at one end of said envelope and extending into the interior of said envelope, and an armature pivotally mounted on said magnetic member, the combination of a first electrically conductive terminal pin extending through the envelope into the interior thereof of which at least the inner extremity of said pin is composed of copper infiltrated tungsten; a second electrically conductive terminal pin extending through the envelope into the interior thereof and having a transverse slot formed at its inner end; a strip-like movable contact mounted on said armature and having one end extending into said slot in said second pin and positioned to make selective contact with said first pin upon pivotal movement of said armature; and a copper infiltrated contact button mounted on said movable contact in position selectively to engage the extremity of said first pin.

2. The combination defined in claim 1 and which in cludes a tubular metallic shield member mounted on said movable contact and surrounding said contact button.

3. The combination defined in claim 1 and which includes an elongated resilient strip member aflixed at one end to said movable contacts and extending into said slot in said second pin to hold said movable contact in engagement with said second pin.

4. The combination defined in claim 1 and which includes a disc-like metallic member concentrically mounted on at least one of said terminal pins adjacent the inner surface of said envelope.

5. In a vacuum relay which includes an envelope, a magnetic member mounted in said envelope, and an armature movably mounted on said magnetic member, the combination of: a first electrically conductive pin extending through the envelope into the interior of the envelope, at least the inner extremity of said pin composed of copper infiltrated tungsten; a second electrically conductive pin extending through said envelope into the interior of said envelope; a movable contact mounted on said armature in electrical contact with said second pin and in position to make selective contact with said first pin upon movement of said armature; and a copper infiltrated button mounted on said movable contact in position selectively to engage the extremity of said first pin.

6. The combination defined in claim 5 and which includes a tubular metallic shield member mounted on said movable contact and surrounding said contact button.

7. In a vacuum relay which includes an envelope, a magnetic member mounted in said envelope, and an armature movably mounted on said magnetic member, the combination of: a first electrically conductive pin extending through the envelope into the interior thereof; a second electrically'conductive pin extending through contact member and extending into said slot in said second pin to hold said movable contact in engagement With said second pin.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner. 

5. IN A VACUUM RELAY WHICH INCLUDES AN ENVELOPE, A MAGNETIC MEMBER MOUNTED IN SAID ENVELOPE, AND AN ARMATURE MOVABLY MOUNTED ON SAID MAGNETIC MEMBER, THE COMBINATION OF: A FIRST ELECTRICALLY CONDUCTIVE PIN EXTENDING THROUGH THE ENVELOPE INTO THE INTERIOR OF THE ENVELOPE, AT LEAST THE INNER EXTREMITY OF SAID PIN COMPOSED OF COPPER INFILTRATED TUNGSTEN; A SECOND ELECTRICALLY CONDUCTIVE PIN EXTENDING THROUGH SAID ENVELOPE INTO THE INTERIOR OF SAID ENVELOPE; A MOVABLE CONTACT MOUNTED ON SAID ARMATURE IN ELECTRICAL CONTACT WITH SAID SECOND PIN AND IN POSITION TO MAKE SELECTIVE CONTACT WITH SAID FIRST PIN UPON MOVEMENT OF SAID ARMATURE; AND A COPPER INFILTRATED BUTTON MOUNTED ON SAID MOVABLE CONTACT IN POSITION SELECTIVELY TO ENGAGE THE EXTREMITY OF SAID FIRST PIN. 